S206: OBINUTUZUMAB PLUS CHEMOTHERAPY DEMONSTRATES LONG-TERM BENEFIT OVER RITUXIMAB PLUS CHEMOTHERAPY IN PATIENTS WITH PREVIOUSLY UNTREATED FOLLICULAR LYMPHOMA: FINAL ANALYSIS OF THE GALLIUM STUDY
Authors: W. Townsend, W. Hiddemann, C. Buske, G. Cartron, D. Cunningham, M. J. Dyer, J. Gribben, E. Phillips, M. Dreyling, J. F. Seymour, A. Grigg, T.-Y. Lin, X.-N. Hong, D. Kingbiel, T. G. Nielsen, A. Knapp, M. Herold, R. Marcus
Journal: HemaSphere (2022)

Background: Immunochemotherapy with rituximab plus chemotherapy (R-chemo) has significantly improved outcomes for patients (pts) with previously untreated follicular lymphoma (FL). However, most pts still experience disease relapse, progression, or death. Obinutuzumab (G) is a type II anti-CD20 monoclonal antibody with enhanced direct cell killing, antibody-dependent cellular cytotoxicity and antibody-dependent phagocytosis versus R. The safety and efficacy of G-chemo versus R-chemo was assessed in pts with previously untreated, advanced stage FL in the randomized, Phase III GALLIUM (NCT01332968) study. In the primary analysis, G-chemo demonstrated a significant improvement in progression-free survival (PFS) versus R-chemo, with a manageable safety profile (Marcus, et al. 2017); this efficacy benefit was maintained after 5 years of observation (Townsend, et al. 2020). Aims: To report the final analysis of the GALLIUM study after a median observation time of 8 years. Methods: Pts aged ≥18 years with previously untreated histologic Grade 1–3a FL requiring treatment were enrolled. Pts were randomized 1:1 to receive G 1000mg intravenously (IV; Days [D]1, 8 and 15 of Cycle 1 and D1 of subsequent cycles) or R 375mg/m2 IV (D1 of each cycle) plus chemo for 6 or 8 cycles depending on the chemo backbone selected at each institution (cyclophosphamide, doxorubicin, vincristine, and prednisolone [CHOP]; cyclophosphamide, vincristine, and prednisolone [CVP]; or bendamustine). Pts attaining a complete or partial response received maintenance with the same antibody every 2 months for 2 years or until disease progression (PD). The primary endpoint was investigator-assessed PFS; secondary endpoints included time-to-next anti-lymphoma treatment (TTNLT), overall survival (OS) and incidence of adverse events (AEs). All pts provided written informed consent. Results: 1202 pts with FL were enrolled (G-chemo, n=601; R-chemo, n=601). As of July 30, 2021, median observation time was 8 years. Seven-year PFS was improved with G-chemo (63.4%) versus R-chemo (55.7%; hazard ratio [HR], 0.77; 95% confidence interval [CI]: 0.64–0.93; p=0.006; Figure). TTNLT was also improved with G-chemo versus R-chemo (HR, 0.71; 95% CI: 0.58–0.87; p=0.001); the proportion of pts who had not started their next treatment at 7 years was 74.1% and 65.4%, respectively. Disease transformation was observed in 4.2% of pts with G-chemo and 5.0% of pts with R-chemo. Seven-year OS was similar in both arms, 88.5% with G-chemo versus 87.2% with R-chemo (HR, 0.86; 95% CI: 0.63–1.18; p=0.36). Seventy-five pts in the G-chemo arm and 86 pts in the R-chemo arm had died, most commonly due to PD (4.2% and 6.0%, respectively). The incidence of serious AEs (SAEs) was 48.9% with G-chemo (28.2% and 24.4% during induction and maintenance, respectively) and 43.4% with R-chemo (24.6% and 21.7%, respectively). Rates of fatal AEs were similar with G-chemo (4.4%) and R-chemo (4.5%); pneumonia was the most common fatal AE (0.8% [n=5] and 0.2% [n=1], respectively) and SAE (5.9% [n=35] and 6.2% [n=37], respectively). Second malignancies occurred in 13.1% of pts in the G-chemo arm and 9.9% of pts in the R-chemo arm. After adjusting for observation time, rates were similar between arms. These safety findings are consistent with previous analyses. Image:Summary/Conclusion: After a median observation time of 8 years, a meaningful improvement in PFS was maintained with G-chemo versus R-chemo in pts with previously untreated FL, confirming the role of G-chemo as a standard of care for the first-line treatment of pts with FL.